In normal extraocular muscle, our objectives are the serial analysis of mammalian extraocular muscle for the purpose of (a) discriminating morphologically distinct populations of muscle fibers in terms of their internal cell structure, innervation, and histochemical profile, and (b) ascertaining the topographical organizations of such fiber populations within the respective extraocular muscles. Emphasis will be placed on morphometric quantification of sarcoplasmic reticulum, myofibrils, and mitochondria, whereby respective fiber populations may be defined and differentiated, and whereby systematic variations along the fiber length may be demonstrated. In abnormal extraocular muscle, our objectives are (a) the analysis of biopsy specimens from cases associated with various neuromuscular syndromes of interest, with emphasis on obtaining insight as to possible myopathic vs. neurogenic primacy, (b) the serial analysis of extra ocular muscles from myotonic mice, as well as from rats in which myotonia is drug-induced, and (c) the serial analysis of denervated extraocular muscle in rat.